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From the category archives: Buildings Technology

Electrical and related buildings technology

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Differential protection, the good old days

This morning I was explaining how differential protection works to a junior engineer. To give him something to read I opened up the NPAG (Network Protection...

DC Component of Asymmetrical Faults

The image (reproduced from IEC 60909) shows a typical fault in an ac system.  From the illustration it can seen that there is an initial dc component ...

Why a Sine Wave?

I received this question by email a few weeks. First thoughts was that it is a product of the mathematics of rotating a straight conductor in a magnetic...

Understanding Motor Duty Rating

One of the comments on my Motor Starting Series was asking for something on duty cycles. Here it is. As a purchaser of a motor, you have responsibility...

Photovoltaic (PV) - Electrical Calculations

Photovoltaic (PV) cells (sometimes called solar cells) convert solar energy into electrical energy.  Every year more and more PV systems are installed...

The dc resistance of conductors

This is the first of two posts on the resistance of conductors. In the next post I will look at the ac resistance, including skin effect and we deal with...

Railway Electrification Voltages

This post is quick introduction and overview to different railway electrification voltages used in answer to a question sent in via email. While there...

110 or 230 Volts

I've been considering a blog on the 110 or 230 Volt issue for a while.  While browsing the Internet I came across a great summary by Borat over at  engineering...

Generator Sizing & Operation Limits

When selecting a generator, there are inherent limits on the active and reactive power which can be delivered. Generators are normally sized for a certain...

Cable Trumps

Bored at work and would rather be playing trump card game with you son. The next best thing (or not) maybe the online cable trump card game from AEI Cables...

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